Quercus cerris

Taxonomy 

Name: Quercus cerris L. (1753)

Common name: Turkey Oak

The genus Quercus is notorious for hybridisation and introgression due to weak reproductive isolation mechanisms; it is also subject to a great deal of study, (e.g. Curtu et al. 2007). Lucombe Oak - Quercus x hispanica ‘Lucombeana’ Sweet ex Loud. (1838) - is such a hybrid between Q. cerris and Q. suber, (Cork Oak) that is grown in many botanic gardens (Trehane 2007; Sterry 2007). Putative hybrids between Q. cerris and Q. robur have been recorded in Britain - currently the subject of an MSc research project, (see further work).

Chromosome No.: 2n = 24 (Stace 2010).

Quercus cerris

Photograph: A.J. Lockton

Identification 

The leaf shape of Q. cerris varies greatly between individuals and on the same tree. Leaf lobing is usually more angular and irregular than Q. robur, commonly cut one-two thirds to the midrib, but can be deeper and very fancily lobed, especially on cut branches e.g. hedges. Leaves usually have mucronate tips to the lobes, and are pubescent with stellate hairs, commonly densely so on their lower surface. It differs from the native Q. robur and Q. petraea in that its buds are surrounded by persistent whisker-like stipules. Fruit cupules are covered by patent to reflexed scales up to 1 cm - in contrast to the two British native oaks (Stace 2010; Mitchell 1976).

Quercus cerris

Whisker-like stipules of Quercus cerris

Photograph: K.J. McGinn

 

Distribution 

Q. cerris is native to S Central and SE Europe, extending into SW Asia (Preston et al. 2002). It is a widely planted tree of parks, gardens and roadsides in Britain, but also seeds freely and has so become naturalised, often occurring in mixed stands alongside the native Q. robur and Q. petraea. This neophyte is most common in the southern half of lowland Britain (Preston et al. 2002).

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

Ecology 

Q. cerris has a fast growth habit, and seemingly tolerates a range of soil types; most common on free draining, sandy and acidic soils, but is also known on calcareous soils (Sterry 2007; Preston et al. 2002). Four non-native cynipid gall wasps, Andricus kollari, A. lignicola, A. quercuscalicis and A. corruptrix, have become established in the British Isles since the introduction of Quercus cerris. Their interesting lifecycles involve host-alternating generations, with a sexual generation on the male flowers of Q. cerris in spring, and an agamic (asexual) generation on the acorn cups of British native oaks, (Q. robur, Q. petraea and their hybrid Q. x rosacea) in autumn, (Schonrogge et al. 2002). Infection results in a reduction in the acorn crop of the British Oaks as development of a sexual gall replaces an acorn, but galling rates have been shown to vary between the gall wasp species over time, and differ greatly between individual trees, (Collins et al. 1983; Schonrogge et al. 2002)

Status 
  • Origin: introduced to Britain by J. Lucombe of Exeter in 1735 (Sterry 2007). Documented in the wild since at least 1905 (Preston et al. 2002).
  • Rarity: widespread and common.
  • Threat: it has a change index of +2.32; a dramatic increase that is partly attributable to better recording of aliens, as well as a genuine increase (Preston et al. 2002).
  • Conservation: no conservation status.
Further Work 

There has been debate over the existence of hybrids between Quercus cerris and the native Q. robur. Specimens have been documented in Britain over the past few decades that have persistent stipules and pubescence  characteristic of Q. cerris, but with leaf lobation more like Q. robur. Although the genus Quercus is notorious for hybridisation, it usually occurs between more closely related species, that is within the same taxonomic group known as sections. Q. cerris and Q. robur are in different sections of subgenus Quercus - section Cerris and section Quercus respectively. A study invloving DNA analysis with nuclear microsatellite markers has provided molecular evidence suggesting these possible hybrids are in fact the pure species, Q. cerris, with confusion seemingly having arisen due to the extreme variability in leaf shape of Q. cerris, (McGinn 2010). This conclusion is supported by the opinions of many botanists in disallowing older records of the putative hybrid, e.g. Stace 2010.

Please contact me, Kevin McGinn (k.j.mcginn@student.reading.ac.uk) for more details.

References 
  • Collins, M., Crawley, M. J. & McGavin, G. C. 1983. Survivorship of the sexual and agamic generations of Andricus quercuscalicis on Quercus cerris and Q. robur. Ecological Entomology, 8: 133-138.
  • Curtu, A.L., Gailing, O. & Finkeldey, R. 2007. Evidence for hybridization and introgression within a species-rich oak (Quercus spp.) community. BMC Evolutionary Biology 7: 218
  • McGinn K. J. (2010) A morphological and molecular study of putative hybrids between Quercus robur and Q. cerris in Britain. MSc Plant Diversity thesis, University of Reading.
  • Mitchell A. 1976. Trees of Britain and Northern Europe. Collins.
  • Schonrogge, K., Walker, P. & Crawley M. J. 1998. Invaders on the Move: Parasitism in the Sexual Galls of Four Alien Gall Wasps in Britain (Hymenoptera: Cynipidae). Biological Sciences, 265: 1643-1650
  • Sterry, P. 2007. Collins Complete British Trees. HarperCollins Publishers.
  • Trehane, P. 2007. The Oak Names Checklist. http://www.oaknames.org

 

Citation 
McGinn, K.J. 2010. Species account: Quercus cerris. Botanical Society of the British Isles, www.bsbi.org.uk.

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